I installed a D3 in my 2000 ML430 and I'm trying to get the most out of it. The schematic is attached. I had assumed the Bose inputs were standard line level and the D3 outputs were standard line level. Not so. Looks like the Bose wants balanced inputs (as opposed to single-ended) and at a level of about double what the D3 is giving it. So as a result, the volume is low compared to the factory MCS radio and there is some noise at the amp.

What are my options? There seem to be many companies making hi-lo line output converters that will attenuate the speaker outputs of the D3 into levels acceptable to the Bose. That doesn't really deal with the balanced input issue though and it also adds two places where more noise is added (D3 amps and the hi-lo converters). Also, why are these converters so huge?

It seems like a better idea would be to add a converter that would take the 2volt single-ended outputs from the D3 and make the +/- 2volt balanced outputs that the Bose wants. Does anything like that exist at a reasonable cost?

AVIC-D3_ML430_v3.pdf

Just play right into it, speaker level. No proplem. There is no combining negatives with positives.

Looks like you just put way too much thought into it.

Looks like you just put way too much thought into it.

Probably true - not like I haven't heard that before.

Are you saying the Bose amp isn't expecting a balanced input? Or just that the D3 speaker outputs can connect directly to this Bose amp and sound good (or at least as good as it sounded with the MCS head unit)? That would be simpler and cheaper than buying or building a balanced line driver. I'd have to be careful not to overdrive the amp though. You seem to have quite a bit of experience. Have you done anything similar?

My girl has a ML and we did harness with amp intergaration and all factory sounds great if not better than original head unit.

The factory deck in your car is high level output, the amps just divide it all up and boost it some.

If your really concerned about overdriving, go to a Best Buy install bay, and ask for the Periphial ISVE-61 premium factory interface. This converter is about the best I have ever seen for quality, and gives you the option to have speaker wires both in and out, the RCA plug is optional.

Then you can manually turn down the converter to your likeing. Don't hook up the black wires on it, just the 8 speaker wires in and 8 speaker wires out.

And yes, I have done ML's before, no issues even without the converter.

Thanks, I'll try that tomorrow (without the converter).

Well, I ran the D3 speaker outputs directly into the Bose amp and it sounds at least as good as with the old MCS - maybe better. The noise floor is also very good again. Obviously that's the best way to do it. Thanks to superjet for suggesting that and Lu Scola for confirming. I'm a happy camper again!